The growing diplomatic scandal over the poisoning of an ex-spy in Britain will not disrupt Russia’s presidential campaign, Vladimir Putin’s spokesman has said.

Dmitry Peskov told reporters on Thursday the nerve agent attack on Sergei Skripal “doesn’t affect” the campaign for Sunday’s election, which he called Russia’s top priority.

He strongly denied Russian responsibility in the March 4 attack.

The Russian campaign remains lacklustre just three days before the vote, and Mr Putin is overwhelmingly expected to win another term after 18 years in power, riding in part on his argument that he must stand up to Western aggressors.

Opposition candidate and former TV star Ksenia Sobchak is holding a big rally on Thursday, after breaking down in tears at the final televised debate Wednesday night. She was the only candidate to criticise Mr Putin.

His self-assurance and relaxed demeanour reflects the stress-free campaign he has run ahead of Sunday’s election that is certain to catapult him to another six-year presidential term.

The victory will put the Russian leader on track to become the nation’s longest-serving ruler since Josef Stalin.

The 65-year-old president has made many trips across the vast country, reaching out to various social groups and industrial sectors.

Unlike the 2012 election, when Mr Putin often looked tense and nervous amid massive protests against his rule, he faces no such threats this year — even with a weak economy and spiralling tensions with the West.

His popularity soared after Russia annexed Ukraine’s Crimean Peninsula in 2014, and his ratings still top 80%, buttressed by flattering coverage of his activities by state-controlled media amid bitter showdowns with the West.